Trichomonas vaginalis, an aerotolerant anaerobe, is a flagellated protozoan parasite which infects the reproductive tracts of both men and women, and causes the most common of the sexually transmitted diseases. Yearly, there are -180 million new patients world wide, with nearly 3 million new cases in the US annually. Although the clinical aspects of human trichomoniasis are being elucidated, a significant gap remains in understanding how the molecular genetics of T. vaginalis relate to strain infectivity and pathogenicity. The overall goal is to further characterize the structural and functional properties of novel ribosomal RNA genes (denoted rDNA*) in this parasitic protozoan. The end point is to relate specific, trackable genomic and biological features of these alternate rRNA genes to the pathogenicity of this parasite. The basic premise of this proposal is that there is an alternate set of rRNA genes in T. vaginalis containing variant small subunit (SSU*) and perhaps large subunit (LSU*) template sequences, and that these genes may code for rRNA species which provide this organism with an important adaptive flexibility as a parasite. (Such an adaptive response exists for the malaria parasite Plasmodium berghei in which alternative genes give rise to stage-specific ribosomes during the parasitic life cycle.) The specific aims are to experimentally describe the nucleotide and genomic structures of these variant rDNA* genes, to determine whether these rDNAS* are transcribed into variant rRNAS* which are processed and packaged into an alternate set of ribosomes, and to compare the features of these variant rDNAS* and rRNAS* with their normal counterparts in T. vaginalis. This information will be sought by employing specialized polymerase chain reaction protocols to display and analyze the parasite s rRNA genes. Gene cloning and DNA sequencing will be used to determine the primary structure of the genes. Sophisticated electrophoretic gels will be employed to fingerprint and compare the rRNA gene structures in test strains and clinical isolates of T. vaginalis.